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In utero transmission of HIV-1 : regulation and selection via the placenta


To investigate various mechanisms involved in transplacental route, as well as the intracellular and extracellular mechanisms regulating HIV-1 vertical transmission, in an effort to explain why the transmission rate is only partial, and the reasons for such a variation between various pandemia area, as well as the role of maternal viral load, the synergistic role of placental trophoblast cells and maternal antibodies in the transmission and/or selection of HIV-1 variants from mothers to their infants.

As the number of HIV+ individuals increases, so does the transmission of HIV-1/HIV-2 from mothers to infants. Albeit the most common contamination occur during delivery, in utero transmission also occurs and might be related to a more severe and rapid progression of the disease in about 20% of infected children. Our groups are focusing on the role of maternal viral load, synergistic role of placental trophoblast cells and maternal antibodies in the transmission and/or selection of HIV-1 variants from mothers to their infants. For this purpose, we have set up a cohort of infected mothers in Cameroon, as well as sample collection in France, Italy. and Greece. The French cohort comprises 10 transmitting mothers and 10 non transmitting mothers, the infectious state of the children being defined by PCR, virus isolation and a clinical follow up of two years. The Italian group of HIV-1 infected mothers, 5 transmitting mothers and 5 non transmitting mothers, the infectious state of the children was defined by PCR and virus isolation at least at two consecutive time points. Finally, we are establishing a cohort of seropositive pregnant women from Cameroon (now half way ), and we collect/prepare on site maternal blood/serum in early, intermediate and late pregnancy, ester) delivery maternal blood, cord blood and later on samples of child blood if HIV+. We also gather placental explants at delivery and prepare placental trophoblast purified as well as explant samples and sections pre-prepared on site for subsequent Electron Microscopy. Material is also collected in Greece.
The clinical status and viral load of the mothers is routinely assessed in all cases, virus isolations are performed for both the mother and the children, and the genotype of the virus assessed as well as maternal sera antibody titers, antigenemia , and neutralising antibodies .
We also prepare for the project placental trophoblast purified suspensions by the Klinman or Guilber/ Wegmann techniques, and routinely use JAR, BeW0, JEG choriocarcinoma.
We will search for non trophoblastic reservoir cells and microlesions correlating with transmission on placental samples from HIV infected mothers as well as for microlesions in syncitium barrier, syncitium thickening as a result of gestational age, parasitic and microbial influences.
We also investigate if maternal antibody/FcR complex enter the intracellular compartment via endocytosis or pit endosome formation, and make attempts to inhibit it.
We will try to induce and characterise a state of differentiation allowing maximal permissivity for HIV-1 from the already differentiated JAR choriocarcinoma cell line and/or primary culture of trophoblasts . We will use the two-hybrid method to detect viral and cell proteins interactions.
We will analyse the selection of maternal HIV-1 viral variants through trophoblastic cells infected in vitro in the presence or not of the serum of the mothers. The viral strains infecting trophoblastic cells after a defined culture period will be compared with early maternal blood ones in an effort to understand the role of placental barrier in selecting the virus strains that ultimately gain access to the foetus, and correlate such a selection process according to viral composition of the primary isolates, and eventual variations in their tissue tropism. Genetic analysis of viral variants selected by trophoblastic cells will be first assessed by way of the heteroduplex mobility assay, and cloning and sequencing of PCR amplified V3 fragments from samples selected with this HMA assay will be performed.
Since in utero transmission of HIV-1 could also occur by transmission of infected cells (monocytes or T cells) from the mother through lesions in the trophoblast that appear at sites of inflammation, we will engage in identification and characterisation of the cell-adhesion molecules involved in the strong adhesion of activated leukocytes to trophoblast in vitro. We will then determine whether expression of binding-associated antigens or monocytes or trophoblasts is up- or down regulated by TNF or by infection with HIV-1. We will try to block cell-mediated infection of trophoblasts by monocytes via antibodies that inhibit adhesion, and such antibodies will be tested to determine whether they can also block infection of trophoblast by monocytes. We will finally search for expression of cell adhesion molecules expressed on the syncytiotrophoblast or on leukocytes attached to the syncytium in the placenta of normal and HIV-infected women by immunohistochemical

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Université de Paris-Sud XI
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132,Avenue de la Porte de Trivaux
92141 Clamart

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